1. Field of the Invention
The present invention relates to an apparatus adjusting and fixing a position of a lens included in an optical pickup of an optical storage medium recording/reproducing apparatus.
2. Description of the Related Art
In general, an optical pickup includes an optical system as shown in FIG. 1. As shown in FIG. 1, an optical system of an optical pickup includes a light source 3 emitting light having a predetermined wavelength, a grating 4 splitting the light input from the light source 3 into the 0th order and ±1st order, a plate type beam splitter 5 changing a proceeding path of the light emitted from the light source 3, a collimating lens 6 concentrating an incident light by changing a divergent light emitted from the light source 3 into a parallel beam, an objective lens 7 forming a light spot on a recording surface of the optical disk 1, a photodetector 9 receiving the light reflected by the recording surface of the optical disk 1 after passing through the objective lens 7, the collimating lens 6, the plate type beam splitter 5, and a concave lens 8 in order and detecting an information signal and an error signal. The concave lens 8 is disposed between the plate type beam splitter 5 and the photodetector 9 and magnifies the size of a light spot received by the photodetector 9.
The concave lens 8 is referred to as a Yo lens and its position is typically adjusted and fixed by a lens position determination apparatus as shown in FIG. 2. The lens position determination apparatus includes a lens holder 30 where the concave lens 8 is mounted, a base 10 supporting the lens holder 30, and a spring member 20 comprising a pair of pressing pieces 21 is coupled to the base 10 and elastically presses the lens holder 30 via the pressing pieces 21 toward the base 10 so that the lens holder 30 closely contacts the base 10. Thus, as the lens holder 30 is pressed by the pressing pieces 21 of the spring member 20 toward an accommodation surface 11 of the base 10, the position of the lens holder 30 is fixed. In this state, to adjust the position of the concave lens 8, an adjustment rod 40 shown in FIG. 2 is inserted in an adjustment groove 31 of the lens holder 30 and moved in directions indicated by an arrow, so that light is focused. When the adjustment rod 40 is removed after focusing, since the pressing piece 21 continues to press the lens holder 30, the changed position of the concave lens 8 is maintained.
However, in the position determination apparatus having the above structure, because the position of the concave lens 8 is adjusted by sliding the lens holder 30 in a state in which the pressing pieces 21 are still pressing the lens holder 30 toward the accommodation surface 11, frictional resistance is great so that the adjustment work is not smoothly performed. When a pressing force of the pressing piece 21 is too much, even if the lens holder 30 can slide horizontally, it slides asymmetrically in vertical and horizontal directions due to the strong frictional resistance of the pressing pieces 21 and therefore may be adjusted to an inclined position. Such an inclined position of the concave lens 8 is an unstable state, preventing formation of an accurate optical path.